See the Definition of a "Plenum" in Article 100; and then see Section 300-22, and Articles 640; 800; and 820 in the 1999 NEC. For those who ask these types of questions on this BB help is always available with specific references to the NEC.

If you don't have a code book you can order one here from the ECN Bookstore.

In the end the rules you really need are in Section 300-22(c)and in each Article that includes references to this section.

I ask because my local Home Depot employees who claim to be electricians told me that any communications cable installed in a commercial building must be plenum rated. (They don't even know what a plenum is). I am aware of the definition of a plenum. And from everything I can find in the code, I only have to use plenum rated cable when installing in a plenum. But, I'm trying to get other input, because, once again, the Home Depot guys sware that that's the rule - ANY commercial wiring.

Have the Home Depot "ulektrishon" look at the data/com wiring in his store.Then, he should either digress, or report the (not a) violation he finds to the local Code Enforcement Officials.You answered the Q yourself in the last part of your 1st post. Unless there's a specific reason (plenum ceiling, etc) to use p-rated cable, it's not required, commercial or not.No more than you'd need sealtite in a dry location.

(On second thought maybe this guy should have any area he's in rated as a plenum. He certainly spouts some hot air!)

Disregard the Home Depot guys..after all, if they were electricians, they wouldn't be working at Home Depot! I suppose that if the commercial above-ceiling space was used as a plenum then the wall board would go all the way up to the top plate..if not, then the stud spaces would be the same air space as the plenum, and plenum rated cable would be required.